docs: def set_backend(self, backend):
          """ Manually set backend after construction. """
  
          self.backend = backend
          self.dagobah_id = self.backend.get_new_dagobah_id()
  
          for job in self.jobs:
              job.backend = backend
              for task in job.tasks.values():
                  task.backend = backend
  
          self.commit(cascade=True)